Gravel roofs are very popular in many areas of the United States, being less expensive than other types of roofs while being quite durable. However, various weather conditions such as high winds and very heavy rains often displace much of the gravel if the gravel is not sealed in place.
This type of roof is generally constructed of one or more layers of tar paper being fixed in a covering relation to the roof sheathing, the paper is then heavily coated with a roofing tar and the gravel is spread thereatop. To prevent the displacement of the gravel, it is sealed. For many years, the sealing has been accomplished by spraying the gravel. This binds the surface of the gravel coat together and while there is some penetration, it is quite limited and generally within one year's time, the gravel begins to loosen and can actually be picked up and crumbled in one's hand. One of the most widely used compounds employed with this spraying technique is marketed under the tradename "LOCK TITE" and is comprised generally of a synthetic base, a powdered plastic material and lime.
The sealing compound of the present invention is comprised of a properly proportioned mixture of portland cement, sand, calcium aluminate cement and water. The method of applying the mixture includes the use of a broom, preferably of the relatively broad push type whereby the mixture is forced through the gravel to the underlying roofing paper and when dried permanently binds the gravel together and to the roofing paper. At least one and preferably two water barrier coats is then applied thereatop, the water barrier coating being comprised of a mixture of masonry cement, lime and water in proper proporations.
Therefore, one of the principal objects of the present invention is to provide a sealing compound particularly for use on gravel roofs which permanently binds the gravel together in a solid mass and to the underlying roofing paper.
Another object of the invention is to mix the sealing compound with a sufficient amount of water to provide a consistency whereby a broom may be employed to spread the mixture over the surface of the gravel while causing it to penetrate therethrough to the underlying roofing paper.
A further object of the present invention is to apply at least one water barrier coating over the sealed roof after it has set and dried.